I have used a homemade nicotine concoction as a last reasort to ward off last years infestation. This year, in preparation, I have been reading up on Predatory Mites, N. Californicus (sp) to be precise.

Two Spotted Spider Mites: They infect the plant and suck the life out of the leaves, one cell at a time. Seems benign enough until you realize that they can multiply in the thousands and it only takes something like 12-24 hours for them to mature given the right conditions (warm, slightly humid (IIRC)).

I've yet to have mite issues with my hops, but i would think your nicotine spray would be a good start. Safer Soap is another good natural insecticide. I've also used a 3 in 1 product - cant recall the brand, perhaps this was safer as well? - which while not strictly "organic" in nature was - with all apologies to Doug Adams - mostly harmless. Stay away from anything systemic and don't use too close to harvest and you should be good though. Let us know what you do and how well it works though. I'm always up for a good natural pest control method

I use commercial grade pesticide to control the mite population then switch to a nicotine base spray when flowers develope.
For other plants near the hops, I fould tomato does wonders to keep away mites and aphids.